The present invention relates generally to semiconductor packaging. More specifically, the invention relates to very low cost micro surface mount device (μSMD) packages and processes for forming such packages.
There are a number of different integrated circuit packaging styles that are commercially available today. One such package style is referred to as a micro surface mount device (μSMD). In general, μSMD packages have a footprint that is on the same scale as the footprint of the dice that they protect. In many applications it is desirable to provide some structures about the die to protect the die from exposure to the environment and/or to protect the die from exposure to ambient light. Therefore, unlike simple flip chip mounted dice, μSMD packages have some level of protection provided around the dice.
There are currently a number of approaches that are used to create μSMD packages. In some applications, the contacts on the μSMD packages are aligned with bond pads on the dice encased therein. In other applications, the contacts are redistributed relative to the contacts on the underlying dice. One conventional approach to μSMD packaging is to place a plurality of dice into corresponding cavities formed in a silicon carrier. A spin-on polymer coating is then applied over the top surface of the wafer. Holes are formed in the polymer coating and deposition processes are used to form a redistribution layer over the polymer coating. Solder bumps are formed over the redistribution layer to facilitate electrical connection to external devices. Although such a packaging approach works well in many cases, both the carriers used in such processes and the redistribution layer formation steps tend to be relatively expensive and thus the overall packaging costs are relatively high. Accordingly, there are ongoing efforts to develop more cost effective micro surface mount device packaging techniques.